Age-related muscle loss is a major public health issue affecting over 30 million Americans, with no viable treatments available to stem about an 8% loss in muscle mass every decade. Preliminary studies with beta-hydroxy-beta-methylbutyrate, arginine, and lysine (HMB/ARG/LYS) indicate a reversal of age-related muscle loss is possible, at least with women. Limited data collection on elderly men suggest HMB/ARG/LYS may not have an effect. The proposed study will expand on these preliminary studies in women to determine whether a combination of HMB, arginine, and lysine is effective in increasing whole body protein synthesis, fat-free mass, strength and functionality in both older adult men and women. Thirty-two subjects (16 men and 16 women) over the age of 65 years will be recruited and will be assigned to an isonitrogenous control treatment (n=16) or to the experimental treatment group (n=l 6) containing HMB (calcium salt), arginine, and lysine daily (HMB/ARG/LYS) for six weeks. Whole body protein turnover, body composition, strength and functionality will be used as measures of effectiveness. It is hypothesized that this mixture will support maximal protein synthesis and minimize proteolysis resulting in an increase in net protein balance. If proven effective in Phase I, the overall objective of Phase II of this research will be to test the long-term (12 month) efficacy of this nutrient mixture to prevent and reverse the loss of muscle mass, strength, and functionality that occurs in older adults.